Aperture sharing for highlight projection

ABSTRACT

A novel projection system includes a base signal source, a highlight signal source, a base/highlight destination, and a shared optical element. A base signal provided by the base source and a highlight signal provided by the highlight source are combined by the shared optical element. In a particular embodiment, the base signal source and the highlight signal source each include a light source, a spatial light modulator, and optics, and the base/highlight destination includes optics and a spatial light modulator. In a more particular embodiment, the base signal source and the highlight source provide spatially modulated lightfields to the shared optical element. In another particular embodiment, the base signal and the highlight signal are modulated by the spatial light modulator of the base/highlight destination after being combined.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/690,602, filed Nov. 21, 2019, which is a continuation of U.S. patentapplication Ser. No. 16/184,788, filed Nov. 8, 2018, now U.S. Pat. No.10,488,746, which claims priority to U.S. Provisional Application No.62/585,596, filed Nov. 14, 2017, all which are hereby incorporated byreference in their entirety.

FIELD OF THE INVENTION

This invention relates generally to image projection systems and moreparticularly to projection systems that combine multiple imagingsignals.

DESCRIPTION OF THE BACKGROUND ART

Projection systems that combine multiple imaging signals are known. Forexample, prior art systems are capable of combining a high dynamic rangesignal with a high brightness signal, to produce a signal having both ahigh dynamic range and a high brightness. However, the prior art systemsare not entirely satisfactory, because they combine the signals on theviewable medium (e.g., a projector screen) and, thus, do not allow foradditional signal manipulation after the two signals have been combined.

Other prior art solutions provide a means for injecting light into aprojection system. However, such systems only introduce homogenous lightfrom solid state sources. Therefore, these solutions do not allow forsignal manipulation before the signals are combined.

Additionally, prior art systems that combine multiple imaging signalshave not been able to satisfactorily generate images having high qualityand high dynamic range while maintaining satisfactory projectionefficiency.

SUMMARY

The present invention overcomes the problems associated with the priorart by providing systems and methods of combining modulated beams withina projection system. The invention facilitates the combination of baseimage beams and highlight beams, resulting in improved image quality anddynamic range at greater efficiency than known systems.

Example methods for generating images are disclosed. One example methodincludes providing a first lightfield to a first modulator andmodulating the first lightfield to form a first modulated lightfield.The example method additionally includes providing a second lightfieldto a second modulator and modulating the second lightfield to form asecond modulated lightfield. The first modulated lightfield and thesecond modulated lightfield are combined to form a combined lightfield,and the combined lightfield is directed toward a third modulator. Theexample method additionally includes modulating the combined lightfieldto form an imaging lightfield.

In a particular example method, the step of combining the firstmodulated lightfield and the second modulated lightfield includesdirecting the first modulated lightfield and the second modulatedlightfield along a common optical path of an on-axis beam combiner.

In an alternate particular method, the step of combining the firstmodulated lightfield and the second modulated lightfield includesdirecting the first modulated lightfield into a first portion of a relayaperture and directing the second modulated lightfield into a secondportion of the relay aperture. The step of directing the first modulatedlightfield into the first portion of the relay aperture can includedirecting the first modulated lightfield toward a reflective surfaceoriented to direct the first modulated lightfield into the first portionof the relay aperture. The step of directing the first modulatedlightfield toward a reflective surface can include positioning thereflective surface in an optical path of the first modulated lightfieldand out of an optical path of the second modulated lightfield. The stepof positioning the reflective surface in an optical path of the firstmodulated lightfield and out of the optical path of the second modulatedlightfield can include positioning the reflective surface adjacent thesecond portion of the relay aperture.

In another example method, the step of directing the first modulatedlightfield toward a reflective surface can include positioning thereflective surface in an optical path of the first modulated lightfieldand in the optical path of the second modulated lightfield. In aparticular example method, the step of positioning the reflectivesurface inside of an optical path of the first modulated lightfield andinside the optical path of the second modulated lightfield includespositioning a mirror including the reflective surface in the opticalpath of the second modulated lightfield. The mirror (back surface)blocks a first portion of the second modulated lightfield to cause thesecond portion of the relay aperture to have an annular shape. Thereflective surface of the mirror defines the first portion of the relayaperture.

Another particular example method additionally includes receiving imagedata, and the step of modulating the first lightfield to form a firstmodulated lightfield includes modulating the first lightfield based atleast in part on the image data. In addition, the step of modulating thesecond lightfield to form a second modulated lightfield includesmodulating the second lightfield based at least in part on the imagedata, and the step of modulating the combined lightfield to form animaging lightfield includes modulating the combined lightfield based atleast in part on the image data.

In another particular example method, the step of modulating the firstlightfield to form a first modulated lightfield can include steeringportions of the first lightfield. In addition, the step of modulatingthe second lightfield to form a second modulated lightfield can includesteering portions of the second lightfield. The step of modulating thecombined lightfield to form an imaging lightfield includes spatiallymodulating the combined lightfield with, for example, a digital mirrordevice.

Systems for generating images (e.g., projection systems) are alsodisclosed. One example system includes a first modulator configured tomodulate a first lightfield, to form a first modulated lightfield, and asecond modulator configured to modulate a second lightfield, to form asecond modulated lightfield. The example system additionally includes anoptical element configured to combine the first modulated lightfield andthe second modulated lightfield to form a combined lightfield. A thirdmodulator is configured to modulate the combined lightfield to form animaging lightfield. In a particular example system, the optical elementdirects the first modulated lightfield and the second modulatedlightfield along a common optical path. In an even more particularsystem, the optical element is a beam combiner.

In another example system, the optical element includes a reflectivesurface oriented to direct the first modulated lightfield along anoptical path of the second modulated lightfield. In a particularembodiment, the reflective surface is positioned in an optical path ofthe first modulated lightfield and outside the optical path of thesecond modulated lightfield. In a more particular example embodiment,the reflective surface is positioned adjacent an aperture, and theoptical path of the second modulated lightfield is directed through theaperture.

In yet another example system, the reflective surface is positionedinside of an optical path of the first modulated lightfield and insidethe optical path of the second modulated lightfield. For example, thereflective surface can be positioned within an aperture, and the opticalpath of the second modulated lightfield can be directed through theaperture.

A disclosed example system additionally incudes a controller connectedto receive image data and to provide a first set of control instructionsto the first modulator, a second set of control instructions to thesecond modulator, and a third set of control instructions to the thirdmodulator. The first modulator modulates the first lightfield responsiveto the first set of control instructions, the second modulator modulatesthe second lightfield responsive to the second set of controlinstructions, and the third modulator modulates the combined lightfieldresponsive to the third set of control instructions. The first set ofcontrol instructions, the second set of control instructions, and thethird set of control instructions are based at least in part on theimage data.

Optionally, in the example systems, at least one of the first modulatorand the second modulator is a beam-steering (e.g., a phase modulating)spatial light modulator, and the third modulator can be the same ordifferent (e.g., a digital mirror device) type of spatial lightmodulator.

Another example method for generating images includes defining a relayaperture for a projection system, allocating a first portion of therelay aperture for a spatially modulated base image beam, and allocatinga second portion of the relay aperture for a spatially modulatedhighlight beam. The method additionally incudes combining the spatiallymodulated base image beam and the spatially modulated highlight imagebeam by directing the spatially modulated base image beam into the firstportion of the relay aperture and directing the spatially modulatedhighlight beam into the second portion of the relay aperture. Aparticular example method additionally incudes defining a projectionaperture for the projection system. The relay aperture has an F-numbergreater than or equal to the F-number of the projection aperture.

In one example method, the first portion of the relay aperture and thesecond portion of the relay aperture are exclusive of each other. Forexample, the first portion of the relay aperture can be immediatelyadjacent the second portion of the relay aperture. In another examplemethod, the first portion of the relay aperture is annular in shape, andthe second portion of the relay aperture is disposed within an innerperimeter of the first portion of the relay aperture.

In an example method, the step of combining the spatially modulated baseimage beam and the spatially modulated highlight image beam includesdirecting the spatially modulated base image beam and the spatiallymodulated highlight beam along non-parallel axes. In a particularexample method, the step of directing the spatially modulated highlightbeam into the second portion of the relay aperture includes positioninga mirror to reflect the spatially modulated highlight beam into thesecond portion of the relay aperture. Alternatively, the step ofcombining the spatially modulated base image beam and the spatiallymodulated highlight image beam can include directing the spatiallymodulated base image beam and the spatially modulated highlight beamalong coincident axes.

In some example methods, the second portion of the relay aperture isde-centered with respect to a system axis of the projection system.Optionally, a total area of the second portion of the relay aperture issmaller than a total area of the first portion of the relay aperture.

In the example methods, at least one of the spatially modulated baseimage beam and the spatially modulated highlight beam is generated witha beam-steering (e.g., phase modulating) spatial light modulator.

Another example system for generating images includes a relay aperture,a light source, a first modulator, first optics, a second modulator, andsecond optics. The relay aperture has a first portion and a secondportion. The light source is configured to generate a first beam and asecond beam. The first modulator is configured to spatially modulate thefirst beam to generate a spatially modulated base image beam. The firstoptics are configured to direct the spatially modulated base image beaminto the first portion of the relay aperture. The second modulator isconfigured to spatially modulate the second beam to generate a spatiallymodulated highlight beam, and the second optics are configured to directthe spatially modulated highlight beam into the second portion of therelay aperture. A particular example system, additionally includes aprojection aperture, and the relay aperture has an F-number greater thanor equal to the F-number of the projection aperture.

In an example system, the first portion of the relay aperture and thesecond portion of the relay aperture are exclusive of each other. Forexample, the first portion of the relay aperture can be adjacent thesecond portion of the relay aperture. In a different example system, thefirst portion of the relay aperture is annular in shape, and the secondportion of the relay aperture is disposed within an inner perimeter ofthe first portion of the relay aperture.

In an example system, the second optics include a reflective surfaceconfigured to direct the spatially modulated highlight beam along ahighlight axis, the first optics are configured to direct the spatiallymodulated base image beam along a base image axis, and the highlightaxis and the base image axis are non-parallel axes. Alternatively, thesecond optics include a reflective surface configured to direct thespatially modulated highlight beam along a highlight axis, the firstoptics are configured to direct the spatially modulated base image beamalong a base image axis, and the highlight axis and the base image axisare coincident axes.

A more particular example system additionally includes a mirrorpositioned to direct the spatially modulated highlight beam into thesecond portion of the relay aperture. The second portion of the relayaperture is de-centered with respect to a system axis of the system, anda total area of the second portion of the relay aperture is smaller thana total area of the first portion of the relay aperture.

In disclosed example systems, at least one of the first modulator andthe second modulator is a beam-steering spatial light modulator.

Another example system for generating images includes a first spatiallight modulator, a second spatial light modulator, a third spatial lightmodulator, and optics. The first spatial light modulator is configuredto generate a first modulated beam infused with a first image. Thesecond spatial light modulator configured to generate a second modulatedbeam infused with a second image different from the first image. Theoptics are configured to simultaneously focus the first image and thesecond image on an image plane of the third spatial light modulator. Atleast one of the first spatial light modulator and the second spatiallight modulator is a beam-steering spatial light modulator.

Another example method for generating images includes producing a firstmodulated beam infused with a first image, producing a second modulatedbeam infused with a second image, and simultaneously focusing the firstimage and the second image on an image plane of a same spatial lightmodulator. The example method additionally includes further modulatingthe first modulated beam and the second modulated beam with the spatiallight modulator to generate an image beam.

Another example system for generating images includes a first spatiallight modulator, a second spatial light modulator, and a third spatiallight modulator. The first spatial light modulator is configured togenerate a first modulated beam infused with a first image. The secondspatial light modulator is configured to generate a second modulatedbeam infused with a second image different from the first image. Theexample system additionally includes means for simultaneously focusingthe first image and the second image on an image plane of the thirdspatial light modulator.

A non-transitory electronically readable medium is also disclosed. Theelectronically readable medium has code embodied therein that, whenexecuted, will cause a projection system to produce a first modulatedbeam infused with a first image, produce a second modulated beam infusedwith a second image, and simultaneously focus the first image and thesecond image on an image plane of a same spatial light modulator. Thecode will additionally cause the projection system to further modulatethe first modulated beam and the second modulated beam with the spatiallight modulator to generate an image beam.

An example extended range projector is also disclosed. The exampleextended range projector includes a main optical path, for transmittingan image, and a highlight optical path, for transmitting highlightilluminations of the image. The example extended range projectoradditionally includes a means for combining the main optical path andthe highlight optical path. In a particular example projector, thehighlight optical path is injected into the main optical path byreflection from outside of the main optical path. In a more particularexample projector, the highlight path is reflected from outside the mainoptical path and inside a circle defined by a radius from a major axisof the main optical path to a nearest corner of the main optical path.In another more particular example projector, the highlight path isreflected from outside the main optical path and inside a circle definedby a radius of a downstream optical element in the main optical path.Optionally, the highlight optical path can be injected into the mainoptical path at a periphery of the main optical path.

In an example projector, the highlight optical path is projected throughat least one optical element shared with the main optical path and is atleast partially outside the main optical path through the opticalelement en route to illuminating a modulating surface of a primarymodulator. Optionally, all light rays of the highlight optical pathilluminate the modulating surface.

In a particular example projector, the means for combining comprises amirror adjacent to the main optical path. The mirror is configured todirect the highlight optical path into and outside the main optical pathin a manner such that portions outside the main optical path ultimatelyconverge with the main optical path. The combined optical pathsilluminate a modulating surface of a primary modulator. The illuminationof the modulating surface can include a registration of the highlightimage and the approximation of the image.

A particular extended range projector additionally includes a controllerconfigured to determine an illumination on each pixel of the primarymodulator comprising the approximation and highlights. The controlleradjusts the modulation of the primary modulator so as to produce thedesired image. In a more particular example extended range projector,the amount of illumination includes an angular component of thehighlight portions of the illumination and the modulation adjustmenttakes into account the angular component.

An example controller for a projector comprising a highlight image and abase image is also disclosed. The controller is configured to determineilluminations amounts corresponding to pixels of a primary modulator.The illuminations comprise a convergence of portions of the base imagemodulated by a base image pre-modulator and portions of the highlightimage modulated by a highlight image pre-modulator different from thebase image pre-modulator. The illumination amounts include where thehighlight image registered with the base image and where the highlightimage converges with the base image within the projector fromessentially parallel to, but completely outside, a light path of thebase image to fully registered with the base image and combined with thebase image at the modulating surface. Optionally, the base modulatorcomprises a different architecture than the highlight modulator. Forexample, one of the base modulator and the highlight modulator cancomprise one of a wavefront modulator and a holographic modulator, andthe other of the base and highlight modulators can comprise an amplitudemodulator. In a particular example controller, the highlight modulatorcomprises a wavefront modulator, and the primary modulator comprises anamplitude modulator.

Another example extended range projector includes a main optical pathfor transmitting an image, and a highlight optical path for transmittinghighlight illuminations of the image. The example projector additionallyincludes means for combining the main optical path and the highlightoptical path. In a particular example projector, the main optical pathcomprises a rectangular aperture, and the means for combining comprisesa combining element outside of the main optical path that does not blockany light of the rectangular aperture and is located on the long side ofthe rectangular aperture.

The combining element can comprise a non-rectangular aperture. Inaddition, the combining element can reflect a relatively small highlightcomprising a spot into the main aperture. The highlight beam can befocused to a small spot where it joins with the main beam. The combiningelement can reflect a highlight projection into the main aperture, andthe highlight projection can include a small but bright area relative tothe overall area of the combined aperture. In a particular exampleprojector, the combining element reflects a highlight projection intothe main aperture, and the highlight projection comprising less than 50%of the combined optical path at a primary modulator of the extendedrange projector.

Another example extended range projector includes a main optical pathfor transmitting an image and a highlight optical path for transmittinghighlight illuminations of the image. The example projector additionallyincludes a means for combining the main optical path and the highlightoptical path. In a particular example projector, the main optical pathcomprises a rectangular aperture, and the highlight optical pathcomprises an aperture smaller than the rectangular aperture andpositioned outside but adjacent to one side of the rectangular aperture.The highlight path and the main optical path utilize the same opticalelements downstream from the means for combining, even before the mainand highlight paths are fully combined. In addition, the highlight pathand the main optical path can utilize the same optical elementsdownstream from the means for combining, even while some portions of thehighlight path remain outside the main optical path.

In any of the disclosed systems and methods, the highlight path and themain optical path can remain not fully combined until impacting aprimary modulator of the extended range projector. When fully combined,the highlight path can be of a different size and or shape than thefully combined paths.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is described with reference to the followingdrawings, wherein like reference numbers denote substantially similarelements:

FIG. 1 is a block diagram showing a projection system adapted to addhighlights to a projected base image;

FIG. 2 is a block diagram showing the projection system of FIG. 1 inmore detail;

FIG. 3 is a perspective view showing an example physical embodiment of aportion of the projection system of FIG. 1 ;

FIG. 4 is a side view showing the portion of the projection system ofFIG. 3 ;

FIG. 5 is a front view showing the shared optical element of theprojection system of FIG. 1 ;

FIG. 6 is a side view showing a portion of an example alternateprojection system;

FIG. 7 is a side view showing the shared optical element and theaperture of FIG. 6 in greater detail;

FIG. 8 is a side view showing a portion of another alternate projectionsystem;

FIG. 9A is a front view showing a shared optical element of FIG. 8 ingreater detail;

FIG. 9B is a front view showing an alternate shared optical element;

FIG. 10 is a flow chart summarizing an example method for addinghighlight illumination to a projected base image;

FIG. 11 is a flowchart summarizing an example method of combining aspatially modulated base image beam and a spatially modulated highlightimage beam; and

FIG. 12 is a flowchart summarizing an example method of generating animage beam.

DETAILED DESCRIPTION

The present invention overcomes the problems associated with the priorart, by providing a system for combining separately modulated lightsignals prior to additional modulation. In the following description,numerous specific details are set forth (e.g., types of modulators,light sources, etc.) in order to provide a thorough understanding of theinvention. Those skilled in the art will recognize, however, that theinvention may be practiced apart from these specific details. In otherinstances, details of well-known projection practices (e.g., image datamanipulation, optics setup, routine optimization, etc.) and componentshave been omitted, so as not to unnecessarily obscure the presentinvention.

FIG. 1 is a block diagram showing a projection system 100 adapted to addhighlight illumination to a projected base image. The highlightillumination increases the maximum intensity levels and dynamic range ofprojection system 100. System 100 includes a base source 102 and ahighlight source 104. Base source 102 is adapted to provide a spatiallymodulated base signal 106 to a shared optical element 108, and highlightsource 104 is adapted to provide a spatially modulated highlight signal110 to optical element 108. Shared optical element 108 combines basesignal 106 and highlight signal 110 to form a combined signal 112, whichis directed toward a base/highlight destination 114. A controller 116 isconnected to receive image/video data from a data source (not shown) andprovide control signals to base source 102, highlight source 104, andbase/highlight destination 114, based at least in part on the receivedimage/video data. Controller 116 provides coordination between thevarious components of projection system 100.

FIG. 2 is a block diagram showing projection system 100 in more detail.Base source 102 includes a light source 202, a pre-modulator 204, andoptics 206. In this particular example embodiment, light source 202 is alaser array, adapted to provide a homogenous lightfield 208 topre-modulator 204. However, light source 202 can optionally be a lightemitting diode (LED), LED array, an arc lamp, another modulator, or anyother suitable light source. Light source 202 also receives controlsignals from controller 116, which cause light source 202 to energize asubset of lasers to provide white light, colored light, and/ortime-multiplexed RGB light to pre-modulator 204. Pre-modulator 204,responsive to control signals (e.g., image data) from controller 116,spatially modulates lightfield 208 to produce base signal 106 (e.g., abeam infused with an image), which is directed toward optics 206. Optics206 focus and/or defocus base signal 106 and direct it toward sharedoptical element 108.

Highlight source 104 includes a highlight light source 210, a highlightmodulator 212, and optics 214. In this example embodiment, highlightlight source 210 is a low-etendue laser array adapted to provide ahomogenous lightfield 216 to highlight modulator 212. Highlight lightsource 210 is substantially similar to light source 202, but can becontrolled independently of light source 202. For example, highlightlight source 210 can be controlled such that lightfield 216 issignificantly dimmer than or a different color than lightfield 208.Highlight modulator 212, responsive to control signals from controller116, spatially modulates lightfield 216 to produce highlight signal 110(e.g., a beam infused with a different image than base signal 106),which is directed toward optics 214. Optics 214 focus and/or defocushighlight signal 110 and direct it toward shared optical element 108.

Shared optical element 108 is an optical element configured to combinebase signal 106 and highlight signal 110. In the example embodiment,shared optical element 108 is a solid object defining an aperture andhaving a reflective surface thereon. The reflective surface ispositioned adjacent to the aperture. At least a portion of base signal106 is directed through the aperture by optics 206 and at least aportion of highlight signal 110 is reflected from the reflectivesurface. Shared optical element 108 is configured such that the portionof base signal 106 directed through the aperture and the portion ofhighlight signal 110 reflected from the reflective surface are directedalong the same or closely positioned optical path (i.e. combined to formcombined signal 112) toward signal destination 114. Shared opticalelement 108 will be described in further detail with reference to FIGS.3, 4, and 5 below.

Base/highlight destination 114 includes optics 216 and a primarymodulator 218. Optics 216 focus and/or defocus combined signal 112 anddirect it toward an image plane of primary modulator 218. Primarymodulator 218 spatially modulates combined signal 112 to generate animaging signal 220, which is directed toward additional projectionoptics or a viewing medium (not shown). Primary modulator 218, as wellas pre-modulator 204 and highlight modulator 212 are spatial lightmodulators (SLMs). In the example embodiment, pre-modulator 204 andhighlight modulator 212 are beam-steering SLMs. Examples of suchbeam-steering SLMs include, but are not limited to,microelectromechanical systems (MEMS) mirror devices, liquid crystalphase modulators, tip-tilt mirror devices, and so on. Additionally,primary modulator 218 is an amplitude modulating SLM. Examples of suchamplitude modulating SLMs include, but are not limited to, digitalmicro-mirror device (DMD), liquid crystal amplitude modulator, and soon. In alternate embodiments any of pre-modulator 204, highlightmodulator 212, and primary modulator 218 can be either beam-steeringmodulators or amplitude modulators, as needed, for a given application.For example, in one particular system, premodulator 204 and primarymodulator 218 are both amplitude modulating SLMs, and highlightmodulator 212 is a beam-steering SLM.

Projection system 100 is capable of generating images having highdynamic range and image quality while maintaining projection efficiency.Because pre-modulator 204 and highlight modulator 212 are beam-steeringmodulators, light can be optimally distributed in base signal 106 andhighlight signal 110. Additionally, highlight source 104 may not berequired to produce many of the desired projection images, andcontroller 116 can provide control signals to cause highlight lightsource 210 to shut off when not required. Similarly, controller 116 canprovide control signals to cause highlight light source 210 (and/orlight source 202) to become dimmer or brighter as needed for particularimages.

FIG. 3 is a perspective view showing a physical embodiment of a portion300 of projection system 100. Portion 300 includes a portion of basesource 102, the entirety of highlight source 104 and signal destination114, and shared optical element 108. Pre-modulator 204 of base source102 is positioned adjacent a prism 302. Pre-modulator 204 receiveslightfield 208 from light source 202 (FIG. 2 ) and spatially modulateslightfield 208 to form base signal 106, which is directed into prism302. Upon exiting prism 302, base signal 106 is transmitted through alens group 304. Together, prism 302 and lens group 304 compose optics206. Lens group 304 transmits base signal 106 toward shared opticalelement 108, which includes an aperture 306, the aperture stop of theoptical system. Base signal 106 passes through aperture 306 and onto asecond lens group 308. Lens group 308 transmits base signal 106 into aprism 310, which directs base signal 106 onto primary modulator 218.Together, lens group 308 and prism 310 compose optics 216.

Although shown as transmissive SLMs for clear illustration,pre-modulator 204 and primary modulator 218 can be, and most likelywould be, reflective SLMs. In addition, although prisms 302 and 310 areshown representationally as cylindrical prisms, the particular shapes ofprisms 302 and 310 can be varied (e.g., could be total internalreflection (TIR) prisms or in multi-color systems could be Philipsprisms) depending on the particular system design. Furthermore, althoughaperture 306 is shown as rectangular, the particular shape of aperture306 could be varied and would most likely be round.

Highlight source 104 provides highlight signal 110 to shared opticalelement 108. A laser source 312 shines laser light constitutinglightfield 216 through a diffuser 314 and onto highlight modulator 212.Diffuser 314 removes laser and/or optical fiber modal noise from thelaser light. Together, laser source 312 and diffuser 314 composehighlight light source 210. Highlight modulator 212 spatially modulateslightfield 216 to generate highlight signal 110 and directs highlightsignal 110 toward a lens group 316. Lens group 316 is oriented to directhighlight signal 110 onto optical element 108, which includes areflective surface 318 (e.g. a tilted mirror) oriented to directhighlight signal 110 toward lens group 308.

Optical element 108 may be located on the Fourier plane of the systemcomprising highlight modulator 212 and lens group 316, and highlightmodulator 212 steers lightfield 216 at relatively small angles. As aresult, the important components of highlight signal 110 are near the DCterm in the Fourier plane. In addition, the lightfield carried byhighlight signal 110 is configured to have a low spatial frequency.Thus, because of these features, reflective surface 318 can berelatively small compared to aperture 306.

Highlight signal 110 is reflected from reflective surface 318, istransmitted through lens group 308 and prism 310, and is focused on animage plane of primary modulator 218. Lens group 308 may need anincreased diameter to accommodate highlight signal 110 being off-centerrelative to aperture 306. Primary modulator 218 spatially modulates thecombination of base signal 106 and highlight signal 110 to form imagingsignal 220, which is directed toward additional projection optics (notshown).

In alternate embodiments it may be desirable to alter the incoming angleof highlight signal 210. In these embodiments, it may be necessary toalter the orientation of reflective surface 318 and/or optical element108. Additionally, it may be desirable to make reflective surface 318and/or optical element 108 adjustable.

Although shown with a single highlight signal 110, system 100 can bemodified to combine base signal 106 with multiple highlight signals 110.For example, system 100 can be modified to combine base beam 106 withseparate red, green, and blue highlight signals via aperture sharing. Inone example embodiment, the red, green, and blue highlight signals canshare reflective surface 318 in a time multiplexed manner. In anotherexample embodiment, a separate reflective surface can be provided foreach of the red, green, and blue (or other color) highlight signals.

FIG. 4 is a side view showing portion 300 of projection system 100. FromFIG. 4 , it can be appreciated that reflective surface 318 is recessedinto optical element 108 and oriented at an angle with respect thereto.A close-up 402 shows a portion of optical element 108, including arecess 404 having reflective surface 318 disposed inside. Optionally,reflective surface 318 can be included in separate mirror disposedimmediately in front (to the right in FIG. 4 ) of optical element 108.Reflective surface 318 is angled to direct light entering the opticalsystem from highlight modulator 212 (at relatively oblique angles)toward lens group 308.

FIG. 5 is a front view of shared optical element 108 (aperture stop) ofprojection system 100. FIG. 5 shows the relative sizes of aperture 306and reflective surface 318, the latter being much smaller than theformer. Because aperture 306 functions as the aperture stop ofprojection system 100 for base signal 106, and highlight signal 110 isfocused onto reflective surface 318, aperture 306 is significantlylarger than reflective surface 318. However, the relative sizes ofreflective surface 318 and aperture 306 are not essential features ofthe present invention. For example, the entirety of optical element 108(aside from aperture 306) could constitute reflective surface 318.Additionally, aperture 306 can be a mechanical aperture having variablesize.

Together, aperture 306 and reflective surface 318 form a relay aperture502 that is shared by base signal 106 and highlight signal 110. Aperture306 forms a first portion 504 of relay aperture 502, and reflectivesurface 318 forms a second portion 506 of relay aperture 502. Directingbase signal 106 through the first portion (aperture 306) of relayaperture 502 and directing highlight signal 110 through (e.g., reflectedfrom) the second portion (reflective surface 318) of relay aperture 502effectively combines the two separately modulated signals 106 and 110(FIG. 4 ).

In this example embodiment, reflective surface 318 occupies only a smallportion of the second portion 506 of relay aperture 502. However, moreof relay aperture 502 can be used if desired. In addition, because aprojection aperture (not shown) of projection system 100 is larger(e.g., has a smaller F-number) than relay aperture 502, relay aperture502 can be expanded up to the size of the projection aperture. Indeed,embodiments of the present invention exploit the size difference betweenaperture 306 and the projection aperture (not shown) to introduce thesecond portion 506 of relay aperture 502, within the size limits of theprojection aperture.

FIG. 6 is a side view of a portion of an alternate projection system600. Projection system 600 is substantially similar to projection system100, except for an alternate shared optical element 602. In system 600,optical element 602 is a beam combining prism (e.g., a TIR prism incombination with an aperture stop. A base signal 604 enters opticalelement 602 from one direction, while a highlight signal 606 entersoptical element 602 from another direction. Base signal 604 andhighlight signal 606 both exit optical element 602 on the same side,traveling generally in the same direction.

In particular embodiments it may be desirable for highlight signal 606to consist of light polarized at a particular orientation (e.g. “s”polarized) when entering optical element 602. In such an embodiment,diffuser 314 can be replaced with a polarizing diffuser or a polarizercan be added somewhere along the optical path of highlight signal 606between optical element 602 and a highlight light source 608.Additionally, it may be desirable to alter the optics between opticalelement 602 and a primary modulator 610, based on the particularcharacteristics of optical element 602 (e.g. size, diffraction index,etc.). For example, alternate relay optics may be desirable should theinclusion of optical element 602 create a significant difference betweenthe image distance of projection system 600 and the image distance ofprojection system 100.

FIG. 7 is a side view showing shared optical element 602 in greaterdetail to define an aperture 702. Base signal 604 passes throughaperture 702 and enters optical element 602 through a side surface 704of optical element 602. Base signal 604 is transmitted through an angledsurface 706 within optical element 602 and exits optical element 602through a second side surface 708, opposite first side surface 704.Highlight signal 606 enters optical element 602 through a top surface710, reflects off of angled surface 706, and exits optical element 602through side surface 708. Optical element 602 discriminates between basesignal 604 and highlight signal 606 based on angle. (i.e. beamscomposing base signal 604 strike angled surface 706 at relatively flatangles, and beams composing highlight signal 606 strike angled surface706 at relatively oblique angles.) Thus, base signal 604 has asignificantly higher transmission than highlight signal 606.Additionally, it may be desirable to apply an optical coating to angledsurface 706 in order to aid transmittance and reflectance of base signal604 and highlight signal 606, respectively.

FIG. 8 is a side view of a portion of an alternate projection system800. Projection system 800 is substantially similar to projection system100, except for an alternate shared optical element 802. In system 800,optical element 802 is an annular aperture stop having a reflectivesurface centered on the optical axis (with respect to base signal 804)of projection system 800. A base signal 804 passes through opticalelement 802 from one direction, while a highlight signal 806 strikesoptical element 802 from another direction. Base signal 804 andhighlight signal 806 are both directed along the same optical path byoptical element 802.

Because optical element 802 directs base signal 804 and highlight signal806 along optical paths that are both symmetric (e.g., parallel,coincident, etc.) with respect to the optical axis of the system, theoptics between optical element 802 and a primary modulator 808 may besmaller compared with those of projection systems 100 and 600.Additionally, because the reflective surface of optical element 802 iscentered in the aperture, it can double as a light dump for lightsteered at small angles.

The annular aperture of optical element 802 may cause projection system800 to have a donut-shaped point spread function (PSF) with respect tobase signal 804, rather than a Gaussian SF, as is typical. Thedonut-shaped PSF can be accommodated for by the lightfield simulationand/or when generating drive values for pre-modulator 810.

FIG. 9A is a front view showing optical element 802 in greater detail.Base signal 804 travels through a large, rectangular, annular aperture902 (between the outer perimeter of aperture 902 and an outer perimeterof a reflective surface 904). Highlight signal 806 reflects off ofreflective surface 904, centered within aperture 902. Together, aperture902 and reflective surface 904 constitute an enlarged aperture stop witha small, central, reflective obscuration. Optical element 802 allowsboth base signal 804 and highlight signal 806 to travel such that theyare symmetric about the optical axis of projection system 800 afterencountering optical element 802.

FIG. 9B is a front view showing an alternate optical element 906. Basesignal 804 travels through a large, circular, annular aperture 908, andhighlight signal 806 reflects off of a reflective surface 910, centeredwithin aperture 908. In alternate embodiments, circular reflectivesurface 910 can be used in combination with rectangular aperture 902,and rectangular reflective surface 904 can be used within circularaperture 908.

FIG. 10 is a flowchart illustrating an example method 1000 for addinghighlight illumination to a projected base image. In a first step 1002,a first lightfield is provided to a first modulator. Next, in a secondstep 1004, the first lightfield is modulated to form a first modulatedlightfield. Then, in a third step 1006, a second lightfield is providedto a second modulator. Next, in a fourth step 1008, the secondlightfield is modulated to form a second modulated lightfield. Then, ina fifth step 1010, the first modulated lightfield and the secondmodulated lightfield are combined to form a combined lightfield. Next,in a sixth step 1012, the combined lightfield is directed toward a thirdmodulator. Finally, in a seventh step 1014, the combined lightfield ismodulated to form an imaging lightfield.

FIG. 11 is a flowchart summarizing an example method 1100 of combining aspatially modulated base image beam and a spatially modulated highlightimage beam. In a first step 1102, a relay aperture is defined for aprojection system. Then, in a second step 1104, a first portion of therelay aperture is allocated for a spatially modulated base image beam.Next, in a third step 1106, a second portion of the relay aperture isallocated for a spatially modulated highlight beam. Then, in a fourthstep 1108 the spatially modulated base image beam and the spatiallymodulated highlight image beam are combined by directing the spatiallymodulated base beam into the first portion of the relay aperture anddirecting the spatially modulated highlight beam into the second portionof the relay aperture.

FIG. 12 is a flowchart summarizing an example method 1200 of generatingan image beam. In a first step 1202, a first modulated beam infused witha first image is produced. In a second step 1204, a second modulatedbeam infused with a second image is produced. Then, in a third step1206, the first image and the second image are simultaneously focused onan image plane of a same spatial light modulator. Then, in a fourth step1208, the first modulated beam and the second modulated beam are furthermodulated with the spatial light modulator on which the first image andthe second image are simultaneously focused.

The description of particular embodiments of the present invention isnow complete. Many of the described features may be substituted, alteredor omitted without departing from the scope of the invention. Forexample, alternate optics (e.g., different types, sizes, numbers oflenses, prisms, mirrors, etc.), may be substituted for optics 206, 214,and 216. In addition, although embodiments of the invention areillustrated using single channel projectors for the sake of simpleexplanation, it should be understood that the present invention can, andmost likely would, be used in multi-channel color projection systems. Inthat case, for example, single modulators (e.g., 204, 212, and/or 218)would each be replaced with a plurality of modulators, one for eachcolor, arranged, for example, in a Philips prism. As yet anotherexample, selectively reflective surfaces can be substituted for thereflective surfaces used to combine the optical paths of a base signaland a highlight signal. Examples of selectively reflective surfacesinclude, but are not limited to, phase and wavelength selectivesurfaces. These and other deviations from the particular embodimentsshown will be apparent to those skilled in the art, particularly in viewof the foregoing disclosure.

We claim:
 1. A method for generating images, comprising: modulating afirst lightfield by a first modulator to form a base modulatedlightfield; modulating a second lightfield by a second modulator to forma highlight modulated lightfield; combining the base modulatedlightfield and the highlight modulated lightfield by a shared opticalelement to form a combined lightfield; and modulating the combinedlightfield by a third modulator to form an imaging lightfield.
 2. Themethod of claim 1, wherein step of combining comprises: directing thebase modulated lightfield by a first portion of the shared opticalelement; and directing the highlight modulated lightfield by a secondportion of the shared optical element.
 3. The method of claim 1, whereinthe shared optical element comprises a relay aperture, and the relayaperture comprises: an aperture configured to direct the base modulatedlightfield through the aperture; and a reflective surface configured toreceive and reflect the highlight modulated lightfield.
 4. The method ofclaim 1, wherein the shared optical element comprises a beam combiningprism, and the beam combining prism comprises a surface configured totransmit the base modulated lightfield and reflect the highlightmodulated lightfield.
 5. The method of claim 1, wherein the sharedoptical element comprises an annular aperture, and the annular aperturecomprises: an aperture configured to direct the base modulatedlightfield through the aperture; and a reflective surface centeredwithin the aperture, the reflective surface configured to receive andreflect the highlight modulated lightfield.
 6. The method of claim 5,wherein the aperture is circular or rectangular, and the reflectivesurface is circular or rectangular.
 7. The method of claim 1, furthercomprising: directing the combined lightfield towards the thirdmodulator by optics.
 8. The method of claim 1, further comprising:generating by a first light source the first light field directedtowards the first modulator; and generating by a second light source thesecond light field directed towards the second modulator.
 9. The methodof claim 1, wherein the highlight modulated lightfield has a low spatialfrequency compared to the base modulated lightfield.